NEW YORK — If Matt Harvey represents everything that bodes well for the Mets starting rotation moving forward, then Jeremy Hefner is the face of everything that is disconcerting about that same unit.

On the heels of one of the most uplifting nights in the brief history of Citi Field authored by Harvey, reality set back in as the bottom of the rotation imploded again.

Hefner, in the rotation because of injuries, served up two more home runs — making it six in his last eight innings — and the Mets bullpen had another meltdown in a 7-6 loss to the Washington Nationals today before 24,325 fans.

"We’re just not making the pitches we have to make," said Mets manager Terry Collins.

Nationals phenom Bryce Harper hit two homers, including a 440-foot blast off reliever Josh Edgin (0-1) in the eighth that broke a tie ballgame and proved to be the game winner.

Washington (10-7) clubbed four homers on the afternoon. Ex-Yankees closer Rafael Soriano pitched the ninth for his sixth save.

After Harvey and Jon Niese, the Mets have little in the way of reliable starting pitching with Johan Santana out for the season and Shaun Marcum recovering from nerve inflammation in his neck.

Furthermore, top pitching prospect Zack Wheeler issued six walks in his Triple-A start in Las Vegas on Friday night and he doesn’t appear close to joining the Mets.

The Mets (8-8) were hoping Hefner would be able to stop the bleeding and maybe steal a victory or two.

Instead, he has become a human launching pad.

He has given up two homers in three innings against Philadelphia, two in one inning in Colorado and two in four innings against the Nationals.

"It’s definitely an issue right now," Hefner said. "It’s something I’m trying to resolve. I’m close. Overall, it was a step in the right direction for me.

"It’s just a little mechanical thing with the way my arm is coming out of my glove and leaving some balls up over the middle. I’m not getting the usual sink or depth on my pitches."

Collins thinks it might be because Hefner, who missed a start, isn’t getting consistent work, in part because of the frigid weather the team has encountered. Hefner (0-2 with a 7.07 ERA) was roughed up for three runs and four hits over just four innings. He walked three and struck out two. Hefner has now allowed a major-league leading seven home runs in 14 innings, last year he allowed only nine homers in 93⅔ innings.

The bullpen offered little relief.

The Mets rallied from behind twice.

In the fourth, they scored five runs off Nationals starter Gio Gonzalez (five runs, five hits in four innings) to turn a 3-0 deficit into a 5-3 lead.

Then, after Adam LaRoche clocked a three-run homer in the fifth off Aaron Laffey, the Mets battled back to tie the score at 6-6 in the seventh inning.

"You score five runs off Gio, you have to win that game," Mets captain David Wright said.

"You get the momentum on your side, you have to find a way to win that game."

Harper slammed Edgin’s first pitch in the eighth inning. The ball hit the signage on the Shea Bridge. It was a monster shot.

"It was a bad pitch," said Edgin, who struck out three batters in 1⅓ innings. "I tried to go away with a four-seamer and it ran back on me.

"Kudos to him. He hit it," he added.

It was Harper’s seventh homer of the season. One night after the Mets hit four homers off Washington pitchers, the Nationals turned the tables with four of their own.

"We have to step it up a little bit (in the starting rotation)," Collins said. "We have to get (Sunday’s starter) Dillon (Gee) more consistent. We haven’t been able to get guys in a situation where they’re feeling comfortable."

Trailing 3-0 in the third inning after Hefner was taken deep twice, the Mets erupted for five runs in the fourth behind a pair of two-run singles by Collin Cogwill and Justin Turner to take a two-run lead. It was the eighth time this season that the Mets have scored four or more runs in an inning.

"You score runs against good teams, you have to put up zeroes," Wright said.